The present invention relates to a process for measuring the size distribution of laminae which are sampled and conveyed by a conveyor after treating raw material for the purpose of controlling the lamina size in a raw material tobacco leaf treatment line.
In a tobacco production process, tobacco leaves, as raw material, are generally separated from one another and flexibility is imparted to the tobacco leaves by application of water and steam by a moisture control machine. Thereafter they are stripped into parenchyma (hereafter referred to as lamina) and veins (hereafter referred to as ribs) and are separated by a separating machine. The laminae are dried to possess a moisture rate of about 12% so that they are prevented from deterioration and from getting moldy during a long preservation. After the dried laminae are packed in a container such as a barrel (the afore-mentioned process is referred to as raw material treatment process), the laminae are preserved for a long time for maturization. The matured laminae are subjected to treatments such as leaf orientation, blending and flavoring and are then cut into cut tobacco leaves.
The tobacco leaves are stripped into laminae and ribs by the rib removing machine in the raw material treatment process. The degree of this stripping process has a great influence upon the yield and the quality of the raw material. That is, since the tobacco leaves are subjected to great mechanical action when the tobacco leaves are stripped into laminae and ribs, frequently the laminae and the ribs are insufficiently stripped or excessively stripped so that the laminae are finely divided, depending upon the physical properties possessed by the tobacco leaves (these physical properties are substantially determined by the moisture and the temperature possessed by the tobacco leaves) and upon the mechanical impact force of the rib removing machine.
It is thus important to control a factor which influences quality, that is, the mechanical impact imparted to the tobacco leaves contained in the rib removing machine so that the impact is at a magnitude suitable for the tobacco leaves.
Presetting of the mechanical impact force heretofore has been manually carried out. Since the physical characteristics inherent to the tobacco leaves largely change depending on the production locations and on the weather of the produced year, it is very difficult to manually adjust the mechanical impact exerted by the rib removing machine to compensate for constantly changing characteristics of the tobacco leaves and to control the lamina size to an optimum value for managing the quality.
The present inventors hve proposed in Japanese Patent Application No. 58-131980 an apparatus for controlling the lamina size in a tobacco raw material treatment process line, comprising means for measuring lamina yielding ratio in the raw material treatment line in which the tobacco leaves, to which moisture and steam are imparted by a moisture control machine, are stripped into laminae and ribs by using a rotary rib removing machine in which mechanical impact imparted to the tobacco leaves may be changed and the laminae and the ribs are then separated from each other by a separating machine and arithmetic operation means into which a measurement signal from the measuring means is applied as a feed back signal and for searching a rotational number of the rotary rib removing machine as a manipulating factor which provides an optimum lamina size, whereby the mechanical impact force in the rib removing machine is automatically controlled in response to the result of treatment of the raw material tobacco leaves to provide an optimum lamina size.
In the afore-mentioned measuring means of the proposed apparatus, the laminae are sampled from the raw material treatment line, and the sampled laminae are spread over a vibration conveyor 1 in width and longitudinal directions as shown in FIG. 1 and, the spread laminae are passed through two vibration sieves, the sieves having 25 mm and 13 mm meshes respectively, to be separated at these steps. The weight of respective screened laminae are measured by three continuous weight meters 4,5 and 6. The lamina yielding ratio are calculated by the arithmetic operation unit 7 upon the basis of the measurement results. Therefore the measuring means has many problems as follows:
(1) The apparatus is large. PA1 (2) Vibration and noise are high. PA1 (3) Laminae are destroyed and to become small. PA1 (4) Much dust is formed. PA1 (5) Lamina size distribution which does not fall in mesh size cannot be obtained. PA1 (6) Measurement error due to water content in tobacco and rib mixture ratio is large. PA1 (7) Measuring is time consuming.
In order to overcome the above-mentioned problems, the size distribution of a lot of laminae having an indeterminate form is continuously measured in simultaneous, non-contact and non-destructive manner.
For this purpose, there is provided a method in which laminae are uniformly spread over a transporting conveyor so that they are not overlapped and the images of the laminae conveyed on the conveyor at predetermined areas are detected by a television camera and the video signal thus obtained is processed to provide the distribution of the lamina size.
Two methods of processing the video signal have heretofore been known. One of them is referred to as a scan (label) method which is used for colouring computer-aided animation. Upon the basis of the video signal, video data including "1" and "0" in response to picture elements are stored in a memory as shown in FIG. 2. The stored video data are scanned horizontally from the upper first line of the frame. A label No. 1 is given to a first continuous "1" region and the scanning is continued to give a label No. 2 to the next continuous "1" region (FIG. 3). Next, the second line is scanned to provide label Nos. "3" and "4" in a manner similar to that in the first line (FIG. 3). Subsequently if the label regions of lines 1 and 2 are continued, a label No. which is the same as that in the first line is given to the second line to unit the labels (FIG. 4). The operation mentioned above is carried out over the entire frame to provide video data as shown in FIG. 5.
In accordance with the video data, the number of picture elements having the same label number are counted to obtain the size of a lamina, that is, the area of a lamina.
The other method is referred to as the border following method which is used for detecting a contour line. The video data (FIG. 6a) which are obtained in a manner similar to the case of FIG. 2 are horizontally scanned from the first upper line. A picture element "1" is provided with a label No. In this case, label number "2" is given (FIG. 6b). A picture element "1" is searched clockwise from a circled picture element above "2" in FIG. 6b. If this is a picture element "1" a label No. 2 is given to this picture element (FIG. 6c). In FIG. 6c similar search is conducted from a black dot picture element. Border following is completed when a circled picture element is found out be repeating the operations in FIGS. 6d to 6f. After detecting the contour line, the number of picture elements encircled by the contour line is counted so that the counts are considered as the area of the lamina.
The former method involves a relatively smaller error than that of the latter which it makes the unification of the labels tedious when the shape of the lamina is complicated. The latter method is capable of determining the area of a complicated shape while it does involve an error when the lamina has a pinhole. Each method has different features. Both algorithms are complicated and the memory capacity required for video data processing is several bits per picture element.
Accordingly both systems are disadvantageous in that a high capacity memory is necessary.